1. Field of the Invention
The present invention relates to a photosensitive composition suitable for production of lithographic printing plates and photoresists. More particularly, the present invention relates to a positive working photosensitive composition having high sensitivity and being capable of forming high-contrast images.
2. Description of the Prior Art
In general, the compositions comprising alkali-soluble resins and naphthoquinone diazide compounds as a photosensitive material have been used as a positive working photosensitive composition.
However, there have recently been filed a variety of patent applications relating to positive working photosensitive compositions using photosensitive materials other than naphthoquinone diazide compounds.
For example, U.S. Pat. No. 3,984,253 describes that polyphthalaldehyde is made sensitive to ultraviolet rays, electron beams and X-rays by adding acid-forming compounds such as a diazonium salt to a photosensitive composition in order to form positive images.
Further, U.S. Pat. No. 4,311,782 describes a radiation sensitive mixture to be used for forming positive relief images, which comprises an acid-forming compound and a polymerizable compound having orthocarboxyIate units which exist periodically in the molecule of the compound.
Furthermore, Japanese Patent Unexamined Published Application (hereinafter referred to as "J. P. KOKAI") No. 59-45439 describes a resist composition comprising a polymer being unstable to acid and having branched groups and a photopolymerizable initiator capable of forming an acid upon exposure to radiation.
In addition, SPIE vol. 920 Advances in Resist Technology and Processing V (1988), page 33 describes a two-component system positive working photosensitive composition which comprises a metal halide of a triphenylphosphonium or diphenyliodonium compound.
With respect to a method for making a sensitive wavelength higher, J. P. KOKAI No. 59-45439 describes on page 2 that positive working photosensitive compositions are made sensitive to a various wavelength ranging from far ultravioIet rays to visible rays and that, in particular, it is possible to form a resist pattern in the wider area of wavelength ranging from ultraviolet rays to visible rays in case of employing a diaryliodonium salt or a triarylphosphonium salt. Further, U.S. Pat. No. 4,760,013 describes that the sensitive wavelength is made higher by varying the structure of onium compounds.
However, any of the foregoing prior art does not disclose photosensitive compositions having a high sensitivity and having photosensitivity to a wide wavelength area.